Articles by Marco Cavalieri

Reconstructing the development of architectural complexes throughout time is often very difficult. Buildings are usually a series of constructive actions, changes from the original project, and collapses and reconstructions due to human actions (such as demolitions) and/or natural disasters (earthquakes, floods, etc.). The building’s structure records all these events, and by using a relief map gives us the chance to understand and decode them. The archaeological relief map is thus supposed to offer a complete and concise documentation. At the same time, it must be enriched with the additional information needed for a more detailed analysis of the archaeological object itself. In the last few years, the introduction and continuous improvements of many instruments (e.g. laser scanners and photogrammetric technologies) have led to a significant qualitative and quantitative change in the recording of material structures. In particular, the possibility of combining different relief technologies - obtaining high resolution, 3D geometrically correct models of buildings or of entire archaeological sites (which could be further investigated thanks to archaeological analysis or other procedures) - has modified the archaeological approach towards the material ‘datum’ and its divulgation. In order to acquire a better knowledge of contemporary technologies, the dissemination of different methodologies - through their application in research contexts - is the best way to transmit and compare them. This article is dedicated to the presentation and detailed analysis of a photogrammetric RGB point-clouds technology, used for the relief of a room during the archaeological excavation at Aiano-Torraccia di Chiusi (San Gimignano, Siena).

During the years 2006-2007, three teams of scientists (archaeologists with geophysicists) detected the archaeological surface of the Late Antique villa at Aiano-Torraccia di Chiusi (Siena, Tuscany) using GPR (Ground Penetrating Radar), Resistivity and Magnetometry. Their aim was to identify archaeological remains and consequently spend less time and money on digging. At the conclusion of the fieldwork and data treatment, they used a CAD program to overlap geophysical and archaeological layers and check geophysical results on archaeological remains. Despite surveys in many other archaeological sites, they obtained few results: surveys located anomalies in less than 1/4 of the archaeological remains excavated in 2008 and 2009. In this paper the authors attempt to analyze (and try to find better solutions for the future) errors in the geophysical surveys caused by incorrect calibration of the database, low accuracy of grid intersections and excessively long grid lines, in relationship to site conditions and the kinds of archaeological remains. These technical problems in fact certainly create a less than optimal operational synergy between archaeologists and geologists during the post-processing of the data: an analysis of these problems may help to improve future projects of this type.

The paper describes the findings of a geo-electric study conducted at the archaeological site of Torraccia di Chiusi (Siena Province) with the use of soil resistivity modelling. In collaboration with the Département d’Archéologie et Histoire de l’Art (Université catholique de Louvain, Belgium) and the Centro di GeoTecnologie (Università degli Studi di Siena), a new, non-invasive instrument, named the OhmMapper, was used for the first time in an archaeological context to provide geophysical sections of the terrain. The aim of the study was to evaluate the nature and distribution of the buried anthropogenic structures and to properly locate them on the map without the necessity of excavating. The site, located in the valley of the Foci river, has been described as a long lasting settlement (III to VII centuries AD, although ceramics dating to the II century BC have been uncovered). The OhmMapper is a capacitively coupled resistivity meter that measures the electrical properties of rocks and soil without ground stakes used in traditional resistivity surveys. A simple coaxial-cable array with transmitter and receiver sections is pulled along the ground either by a single person or attached to an all-terrain vehicle. The dipole-dipole configuration enables the instrument to immediately pick up the horizontal variations in resistivity, thereby enabling the user to identify structures such as walls or cavities. With the OhmMapper, nine sections were made around the perimeter of the area already excavated to collect data on the presence, depth, and dimensions of anthropogenic structures. The results from the sections were refined and placed on a map using an ArcGIS platform. The interpretation of the nine sections resulted in a new hypothesis on the buried anthropogenic structures and a new model of the natural landscape that existed at the site prior to its construction.